If your RAM isn't large enough to support some of the heavy graphical activity, there is a trick you can play to make up for this. Windows has an option which uses some space from your hardisk as your RAM and helps you inpushing the boundaries while working on your computer. Here's how you have to do it:
Increasing Virtual MEmory(To fasten up your 3d Applications).
1>>Right Click The Computer Icon.
2>>Click Properties.
3>>You'll see a few tabs.Click "Advanced".
4>>Now, Three more options, Click "Settings", Under The Performance option.
5>>Now, you'll see "Virtual Memory" at the bottom of the page.Here is the "Change" option.Click it.
6>>You'll see "Paging File Size fo selected drive".Under it are two more options "INITIAL SIZE", "MAXIMUM SIZE".
7>>IMPORTANT: If you have 512 MB Ram, Then multiply it by 1.5.Whatever PHYSICAL MEMORY you have, multiply it by 1.5.
8>>Now, The result you get after the calculation(For 512 MB, Allocate 768 MB in both the spaces.
9>>Click "SET".
10>>Click OK.
You've increased your Virtual Memory!
Note: Windows doesn't delete the temporary files it creates while using the Virtual Memory. So it's advised to regularly clean up these files it creates using a good trash cleaning utility such as CCleaner.